Conventionally, there is known a display device, such as a head-up display, which makes a user view an image as a virtual image from a position (eye point) of eyes of the user. For example, Patent Reference 1 proposes a technique of providing two concave mirrors for magnifying the image on a light path from an image displaying device to an observer to form a virtual image by reflecting the image of the image display device twice, thereby improving a magnification ratio of the virtual image and geometric distortion of the virtual image. Also, for example, Patent Reference 2 proposes a visual display device which includes: a projection optical system including at least one rotation-asymmetrical correction optical surface for correcting image distortion, wherein a display surface of an image display element and a projection surface of the projection optical system are eccentric in a Y-Z sectional surface and the projection surface is formed by an arc-like curved surface whose bowstring is directed to the projection optical system side in the X-Z sectional surface; and an ocular optical system having a positive reflection power making a distant virtual image from the projected image.
Further, technique relevant to the present invention is proposed in Patent Reference 3, for example.